Home Forums Reloading Big Game Rifles Cratered and Pierced Primers - Advice Needed

JackAZ

You are using CCI 400 primers with a cup thickness of .020 and would be much better off using primer cups of .025 thickness.

Question, how are you sizing your cases, meaning minimum shoulder bump of .001 to .002 or sizing the case with the press reaching cam over and maximum shoulder setback.

Over resizing your cases creating excessive head clearance and thin primer cups could be causing your pierced primers.

When you push the case shoulder back too far your create excess head clearance at the rear of the case. This allows the firing pin to act like a cookie cutter and punch the center out of the primer as the primer moves to the rear and contact the bolt face.



Below a case fired in a AR15 rifle, the primer cup was too thin and the case shoulder was pushed back too far. The AR15 rifle is over gassed and the bolt can move to the rear while there is still pressure in the barrel. And this allowed the primers anvil to poke through the hole in the primer.



I would advise getting the Hornady Cartridge Case Headspace Gauge to control shoulder bump.

Below a fired case from my AR15 carbine.



And the same case after sizing and .003 shoulder bump.



NOTE: I have a Lee full length .223 die if set up as per the instructions and reaching press cam over will push the shoulder back .011 shorter than its fired length. So watch your shoulder bump.